In general, a display device is required to have a viewing angle characteristic (wide viewing angle characteristic) that allows a sharp image to be viewed from a larger number of viewing points. However, depending on an operation environment, it may be preferable that only a user can view displayed contents. It is highly likely that, for example, a laptop computer, a mobile information terminal (PDA: Personal Data Assistant), or a mobile phone is used in a place, such as a train or an airplane, where the general public is present. In such an operation environment, in view of security protection or privacy protection, it is desirable that the display device takes a viewing angle characteristic (a narrow viewing angle characteristic) with which only a user can view a displayed image (from a limited viewing point) and the surrounding people cannot view the displayed image (from other viewing points).
Recently, it is demanded that one display device is provided with capability of switching between a wide viewing angle characteristic and a narrow viewing angle characteristic.
In response to such a demand, for example, Patent Document 1 discloses a liquid crystal display device in which: a viewing-angle-control liquid crystal panel is provided above a display liquid crystal panel; the viewing-angle-control liquid crystal panel and the display liquid crystal panel are sandwiched by two polarizing plates; and a viewing angle characteristic is controlled by adjusting a voltage that is applied to the viewing-angle-control liquid crystal panel, so that a viewing angle characteristic is controlled.
[Patent Document 1]
Japanese Unexamined Patent Application No. 268251/1998 (Tokukaihei 10-268251) (published on Oct. 9, 1998)